Capacitive touch-plate switch for household appliances - has diode and extra RC circuit to prevent RF interference disabling switch

摘要

The interference, caused by RF radiation, is eliminated in a capacitive touch-plate switch by incorporating a reverse-biased diode (D1) in the line leading to the input of the comparator (4) that detects when the switch has been operated. The junction between the diode and the comparator's input is connected via a resistor (R1) to an extra dc voltage (U=). A capacitor (C1) is connected in series with this resistor. By an appropriate choice of values for the resistor, capacitor and the resistor (RD), forming a differentiator with the touch-plate capacitance (CT), RF interference picked up by the user's body is prevented from disabling the switch.